Multi-mode photonic microchip resonator with response in visible wavelength range: theoretical modelling followed by detailed statistical robustness assessment

A compact photonic micro-cavity chip is introduced for high-precision wavelength control. The chip consists of a fused silica central core placed between two photonic crystal mirrors, with dye-filled spacer layers that actively amplify light for improving spectral sharpness and quality. The platform allows precise tuning of the transmission peaks by adjusting not only the crystal features but also using the core’s refractive index profile. For this purpose, three cavity structures, featuring central core layers with uniform, linear, and parabolic refractive index profiles, are designed and analyzed using the characteristic matrix method. Q-factor, finesse, and mode volume were calculated to evaluate resonance quality and provide a basis for design comparison and practical applicability. To address the real-world manufacturing variations, results’ reliability were further tested using Monte Carlo simulations. Three key metrics, spectral correlation coefficient (SCC), spectral fidelity index (SFI), and peak position stability (PPS) were analyzed under different tolerance conditions. Results show that while all the proposed cavities have strong potential for the considered aim, the one with a linearly graded refractive index in the defect layer performs the best.